The broad aim of this proposal is to understand how several key genes of herpes simplex virus are regulated in the latent state. Using a number of recombinant viruses and establishing acute and latent infections in mouse ganglia, this proposal will the regulation of genes encoding the LAT transcript, and the genes for ICPO and ICP4 proteins. The procedures will emphasize the expression during latency, rather than in tissue culture. A part of this proposal is to understand how the LAT gene is transcribed, processed, and transported to the cytoplasm. A second part of this proposal is to determine the location of the promoter and the elements important for its transcription in neurons. An important set of promoters not transcribed during latency is the set of immediate-early promoters. The reason for their lack of transcription will be investigated. Finally, it is proposed to alter the expression of two important immediate-early genes during latency. Using promoters which are active in neurons, the genes for ICPO and ICP4 will be expressed and the phenotype of each recombinant virus during latency will be evaluated. These studies should facilitate an understanding of the mechanisms which are operating during a latent infection. The long term goal of these studies is to understand the molecular basis for the mechanisms which regulate the establishment, maintenance, and reactivation the latent state.